Lubricant stick formulations

ABSTRACT

A solid lubricant formulation useful for lubricating the flanges of locomotive wheels, railcar wheels, rail tracks and in applications where it is desirable to reduce friction when metal contacts metal. The solid lubricant formulation including at least one non-polylactic acid-based polymeric carrier, at least one polylactic acid-based polymer, and at least one lubricant powder.

PRIORITY/CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation application of application Ser. No. 11/295,711, filed Dec. 5, 2005, which was a nonprovisional application of U.S. Provisional Application No. 60/633,279 filed Dec. 3, 2004. Application Ser. No. 11/295,711, filed Dec. 5, 2005 was also a continuation-in-part of application Ser. No. 10/655,082, filed Sep. 3, 2003, which was a divisional of application Ser. No. 10/123,001, filed Apr. 11, 2002, which issued as U.S. Pat. No. 6,649,573 on Nov. 18, 2003, which was a nonprovisional of U.S. Provisional Application No. 60/283,869, filed Apr. 13, 2001. The disclosures of these applications are incorporated by reference.

TECHNICAL FIELD

The present invention generally relates to stick lubricants and more particularly relates to natural based stick lubricants for railroad applications.

BACKGROUND

For over fifty years heavy haul railroads have used a variety of methods to reduce friction between the locomotive/railcar wheel flanges and the gauge face of the rail with which it comes in contact. Railroads and transits have realized they can save substantial amounts of money in lowered maintenance and equipment replacements if lubrication is applied.

Several methods have been used including one method wherein hundreds of wayside lubricators eject hydrocarbon petroleum based lubricants onto the gauge face of the rail as the train travels through a curve. A second method for applying lubricant has been to use track inspection trucks to spray petroleum or synthetic grease onto the gauge face of the track as the inspection truck goes through a curve. A third method is to apply lubricant to the wheel flange of the locomotive whereupon the lubricant gets transferred from the wheel flange of the locomotive to the wheel flange of railcars. Lubricant is then passed back through the train as successive wheels come in contact with the rail and pick up some of the lubricant.

These types of lubrication are typically accomplished by spray devices that squirt small amounts of lubricating oil onto wheel flanges. There are inherent problems with the above-described methods of applying lubricant. First, sprayed oil has a tendency to migrate to the tread of the wheel, making it more difficult for the train to stop. Also, grease and oil on top of the rail can cause the train wheels to slip, inhibiting the ability of the brakes of the train to slow or stop the train. In addition, grease and oil on top of the rail can make it difficult for the train to gain traction from a stopped position or when climbing an incline. Secondly, to keep oil spray devices in working order, it requires excessive maintenance time and expense.

An alternative method for overcoming problems with spraying oil onto the wheel flange of the locomotive or railcar has been to use a solid lubricant stick or rod. The stick or rod is inserted into a tube that is then applied by various mechanical means to the flanges of the wheel of a locomotive or railcar via friction.

Prior art solid lubricants also have inherent problems. First, prior art lubricant sticks contain graphite or molybdenum powders because of their anti-wear properties. These prior art molybdenum disulfide compound sticks were made without polymers whereby the molybdenum disulfide was smashed together in a foil wrapper. However, this made the lubricant stick very hard and brittle, so that they could not withstand a rugged locomotive or railcar environment and the sticks would break or disappear.

Prior art solid lubricant stick compositions also have used polymeric carriers to provide durability, but have also included materials that do not provide extreme pressure anti-wear protection or are potentially hazardous to the environment. In some prior art, the sticks have promoted the ability to lubricate a particular wheel flange, but because they have not contained additives to withstand the extreme pressure of a locomotive or railcar flange against the track, the lubricant has not transferred throughout the train. In other prior art, the solid lubricant has lubricated throughout the train, but these formulas contain undesirable hazardous metallic powders, because of their anti-wear capabilities, but the metallic powders not only pollute the environment, but also may be hazardous to railroad workers.

In other prior art sticks, the lubricant is embedded within a polymeric carrier (typically a petroleum based polymer such as polyethylene), this polymeric carrier stick pressed against the wheel flange for wearing off and application of lubricant there-to. An example of such a lubricant stick is Applicant's patent (U.S. Pat. No. 6,649,573) for a solid lubricant and composition.

Other prior art patents include the following. U.S. Pat. No. 3,537,819 to Davis, et al., discloses that the characteristics of the solid lubricant such as hardness, deposition and rigidity are dependant on the molecular weight and the amount of high molecular weight polyethylene that is used. U.S. Pat. No. 3,541,011 to Davis, et al., also discloses a solid lubricant whereby the characteristics of the lubricant such as hardness, deposition and rigidity are dependent on the molecular weight and on the amount used of high molecular weight polyethylene. U.S. Pat. No. 3,729,415 to Davis, et al., discloses a combination of polyethylene and hydrocarbon oil in a stick lubricant that does not contain extreme anti-wear materials to prevent excessive wear. U.S. Pat. No. 4,915,856 to Jamison discloses an alternative solid polymeric stick formula, which includes lead and other metallic powder in either single or co-extruded compositions. While the metallic powder offers anti-wear properties, it also can pollute the environment, such as ground water, when it drops alongside and also can present hazardous conditions for rail workers. Inclusion of metallic powders, which may be considered hazardous by the E.P.A., is undesirable to railroads and transits.

Still other advantages of the present invention will become readily apparent to those skilled in this art from the following detailed description wherein I have shown and described only the preferred embodiment of the invention, simply by way of illustration of the best mode contemplated by carrying out my invention. As will be realized, the invention is capable of modification in various obvious respects all without departing from the invention. Accordingly, the description of the preferred embodiment is to be regarded as illustrative in nature, and not as restrictive.

SUMMARY OF THE DISCLOSURE

Several exemplary solid lubricant stick formulations are described herein, as are lubricant sticks made from such exemplary formulations, as are exemplary methods of making lubricant sticks. Exemplary processes of manufacturing a lubricant sticks are also described.

An exemplary solid lubricant stick formulation comprises from about 15% to about 70% by volume of a polymeric carrier, 10% to 15% by volume of cornstarch or other complex carbohydrate, 5% to 75% percent by volume of organic and inorganic extreme pressure additives (preferably including an organic and inorganic powder lubricant), optionally a synthetic extreme pressure anti-wear liquid oil, and optionally an optical brightener so that the lubricant can be seen under black light conditions to allow verification that the lubricant is coating the surface to which it is applied.

Another exemplary solid lubricant stick formulation comprises from about 20% to about 70% by volume of at least one polymeric carrier (preferably a polylactic acid-based polymer such as polyactide (PLA)); from about 5% to about 75% by volume of at least one lubricant powder; from about 0% to about 20% by volume of at least one synthetic extreme pressure anti-wear liquid oil; and from about 0% to about 1% by volume of an optical brightener.

Additional understanding of the devices and methods contemplated and/or claimed by the inventor can be gained by reviewing the detailed description of exemplary devices and methods, presented below.

DETAILED DESCRIPTION

The following description provides illustrative examples of that which the inventor regards as his invention. As such, the embodiments discussed herein are merely exemplary in nature and are not intended to limit the scope of the invention, or its protection, in any manner. Rather, the description and illustration of these embodiments serve to enable a person of ordinary skill in the relevant art to practice the invention.

The use of “e.g.,” “etc,” “for instance,” “in example,” and “or” and grammatically related terms indicates non-exclusive alternatives without limitation, unless otherwise noted. The use of “including” and grammatically related terms means “including, but not limited to,” unless otherwise noted. The use of the articles “a,” “an” and “the” are meant to be interpreted as referring to the singular as well as the plural, unless the context clearly dictates otherwise. Thus, for example, reference to “a polymeric carrier” includes two or more such polymeric carriers, and the like. The use of “exemplary” means “an example of” and is not intended to convey a meaning of an ideal or preferred embodiment.

The exemplary lubricant stick formulations include a polymeric carrier. Suitable polymeric carriers include but are not limited to: polylactic acid-based polymers, other “natural” polymers and biopolymers, polyethylene, polypropylene, methylpentene, polyolefins and/or synthetic waxes. One or more of the polymeric carriers used in exemplary lubricant stick formulations could comprise polyactide (also referred to as “PLA,” and as polylactic acid-based polymers/fibers), such as the polymer produced by Cargill Dow LLC and sold under the trade name NATUREWORKS®. PLA is made from lactic acid, this lactic acid typically made from dextrose (made from cornstarch, wheat, sugar beets, dairy products, etc.) by fermentation or chemical synthesis. PLA is a biodegradable thermoplastic that in the environment can degrade within a matter of weeks. By using PLA as some or all of the polymeric carrier used, lubricant sticks made from exemplary lubricant stick formulations are more environmentally friendly.

Preferably, the polymeric carrier begins in one of two forms: powder form or pellet form. When in a pellet form, the pellets are usually between 0.1 and 0.15 inch and are irregularly shaped, or in ball, cylinder or hexagon shapes.

The lubricant stick formulation comprising at least one polymeric carrier and at least one lubricant powder (e.g., a combination of about 80% molybdenum disulfide powder, and 20% graphite powder).

The at least one lubricant powder serves as an anti-wear additive. The at least one lubricant powder comprising 5% to 75% by volume of the formulation of the lubricant stick. In one exemplary lubricant formulation, the at least one lubricant powder comprises a minimum of about 65% by volume of one or more of inorganic molybdenum disulfide powder, graphite powder, talc powder, mica powder or calcium carbonate powder. The significant percentage of these extreme pressure anti-wear powders provides the lubrication necessary to prevent excessive wear due to rolling and sliding contact between wheel flanges of a locomotive and rail track.

Optionally, at least one synthetic extreme pressure anti-wear liquid oil can be included. When liquid oil is used in a formulation, the amount of liquid oil used may vary from 0% to about 20% by volume of the composition. More than one type of liquid oil can be used and the percentage used can be varied depending on the percentage of inorganic or organic powders used, in example, the percentage of liquid oil can be varied depending on the percentage of liquid oil or oils needed for blending of the dry powdered materials. The synthetic liquid oil acts as an extreme pressure anti-wear additive. The preferred synthetic liquid oil is a biodegradable mineral-based oil that assists in the blending of the polymeric carrier and the extreme pressure anti-wear powders. Natural oils, including but not limited to corn oil and soybean oil, could likewise be used. A preferred ratio of about four parts per hundred to about fifteen parts per hundred of the oil can be used. In one exemplary formulation, about 5% by volume of oil is the most effective. Less than 4% of oil by volume in the formulation is not sufficient to contribute to the mixing of the anti-wear powders and the polymeric resin of the polymeric carrier and is thus less preferred.

Optionally, an optical brightener can be included. The purpose of using an optical brightener is so that by using a black light, the lubricant deposition on wheel flanges or rail track can be verified. The optical brightener allows the lubricant to be seen under black light conditions (one could shine a black light onto the railcar flange to see if the lubricant stick was applying lubricant to the flange). The optical brightener therefore verifies that the solid lubricant is coating the surface to which it is being applied. About 1% by volume of optical brightener is preferred in the formulation to ensure visibility, however 0% to about 1% by volume may be utilized.

A first exemplary lubricant stick formulation comprises from about 25% to about 70% by volume of at least one polymeric carrier; from about 5% to about 75% by volume of at least one lubricant powder; from about 0% to about 20% by volume of at least one synthetic extreme pressure anti-wear liquid oil; and from about 0% to about 1% by volume of an optical brightener.

A second exemplary lubricant stick formulation comprises from about 25% to about 50% by volume of at least one polymeric carrier; 0% to 20% of an impact modifier; from about 5% to about 75% by volume of at least one lubricant powder; from about 0% to about 20% by volume of at least one synthetic extreme pressure anti-wear liquid oil; and from about 0% to about 1% by volume of an optical brightener. The impact modifier is preferably derived from the same natural material as the polymeric carrier. The impact modifier is for making the lubricant stick, as formed, less brittle.

A third exemplary lubricant stick formulation comprises from about 25% to about 70% by volume of at least one polymeric carrier, where a portion of said polymeric carrier comprises a polylactic acid-based polymer such as polyactide (PLA), more preferably 10% PLA; from about 5% to about 75% by volume of at least one lubricant powder; from about 0% to about 20% by volume of at least one synthetic extreme pressure anti-wear liquid oil; and from about 0% to about 1% by volume of an optical brightener.

A fourth exemplary lubricant stick formulation comprises from about 25% to about 50% by volume of at least one polymeric carrier, where a portion of said polymeric carrier comprises a polylactic acid-based polymer such as polyactide (PLA), more preferably 10% PLA; 0% to 20% of an impact modifier; from about 5% to about 75% by volume of at least one lubricant powder; from about 0% to about 20% by volume of at least one synthetic extreme pressure anti-wear liquid oil; and from about 0% to about 1% by volume of an optical brightener. The impact modifier is preferably derived from the same natural material as the polymeric carrier. The impact modifier is for making the lubricant stick, as formed, less brittle.

The replacement of a portion of the polymeric carrier with cornstarch (or other complex carbohydrate) results in the remnants (the portion that wears off on the wheel flange (as the lubricant is applied to the wheel flange)) of polymeric carrier, which fall onto the ground breaking down considerably faster than without such an additive. While the amount of polymeric carrier (such as polyethylene) that becomes littered along the railway is minuscule, it never hurts to be more environmentally conscious (whether it is through adding cornstarch or using PLA) and through using embodiments of the present invention that is accomplished. Thus, a fifth exemplary lubricant stick formulation comprises from about 25% to about 70% by volume of at least one polymeric carrier; 0% to about 70% of a complex carbohydrate; from about 5% to about 75% by volume of at least one lubricant powder; from about 0% to about 20% by volume of at least one synthetic extreme pressure anti-wear liquid oil; and from about 0% to about 1% by volume of an optical brightener.

My prior patent (U.S. Pat. No. 6,649,573) discloses the use of a one and/or two part stick formulation. The present invention includes any use of PLA in a lubricant stick, both one part and two part (or more) stick formulations. Thus, the first portion could include PLA, the second portion could include PLA, both portions could include PLA and/or a stick having a single portion could include PLA.

Other combinations of these and other ingredients will be obvious to one skilled in the art and the above formulation is given by way of illustration only. For example, the percentage of polymeric carrier(s) used can vary according to how quickly or slowly a user desires the solid lubricant be deposited against a steel surface. Likewise, the percentage of inorganic powder (such as molybdenum disulfide) can vary depending on how much organic powder (such as graphite) is used, and likewise, the percentage of organic powder used can vary depending on how much inorganic powder is used.

In an first exemplary process of manufacturing a lubricant stick, the exemplary process comprises blending the components of the formulation (e.g., polymeric carrier, lubricant, oil, optical brightener), extruding the formulation (e.g., into pellet size shapes), forming a solid lubricant stick (e.g., via extrusion, transfer molding, injection molding).

In a second exemplary process of manufacturing a lubricant stick, the exemplary process comprises blending (e.g., mixing very well with a heavy duty mixer that confines dust, other manners of pelletizing the ingredients that keeps dust from flying freely) the components of the formulation (e.g., polymeric carrier, lubricant, oil, optical brightener), and forming a solid lubricant stick (e.g., via extrusion, transfer molding, injection molding).

Any suitable compounds can be used to form the formulation, and a skilled artisan will be able to select appropriate compounds for an exemplary formulation according to a particular embodiment based on various considerations, including the surfaces the lubricant is intended to be used on, and the environmental conditions the lubricant is expected to be exposed to. Compounds hereinafter discovered and/or developed that are determined to be suitable for use in lubricant formulations would also be considered suitable for use in a lubricant formulation according to a particular embodiment.

The foregoing detailed description provides exemplary embodiments of the invention and includes the best mode for practicing the invention. The description of these embodiments is intended only to provide examples of the invention, and not to limit the scope of the invention, or its protection, in any manner. 

1. A solid lubricant composition comprising at least one polylactic acid-based polymer and at least one lubricant powder, said composition further comprising: (a) from about 5% to about 55% by volume of at least one non-polylactic acid-based polymeric carrier; (b) about 10% to about 15% by volume of said polylactic acid-based polymer; (c) from about 5% to about 75% by volume of said at least one lubricant powder; (d) from 0% to about 20% by volume of at least one synthetic extreme pressure anti-wear liquid oil; and (e) from 0% to about 1% by volume of at least one optical brightener.
 2. The solid lubricant composition of claim 1, consisting of about 10% by volume of said polylactic acid-based polymer, and 10% to 15% by volume of a complex carbohydrate.
 3. The solid lubricant composition of claim 1, consisting of about 10% by volume of said polylactic acid-based polymer.
 4. The solid lubricant composition of claim 1, comprising 10% to 15% by volume of a complex carbohydrate.
 5. The solid lubricant composition of claim 1, wherein said lubricant powder is selected from one or more of the group consisting of graphite and molybdenum disulfide.
 6. The solid lubricant composition of claim 5, wherein said lubricant powder comprises a mixture of graphite and molybdenum disulfide.
 7. The solid lubricant composition of claim 6, wherein said lubricant powder consists of a mixture of 5 parts of molybdenum disulfide powder and 1 part graphite powder, by volume.
 8. The solid lubricant composition of claim 1, consisting of 60% to 65% by volume said lubricant powder.
 9. The solid lubricant composition of claim 1, wherein said lubricant powder is selected from one or more of the group consisting of graphite, molybdenum disulfide, talc, mica, and calcium carbonate.
 10. The solid lubricant composition of claim 1, comprising 0% to 20% by weight of an impact modifier.
 11. The solid lubricant composition of claim 1, consisting of about 1% to about 5% by volume of said synthetic extreme pressure anti-wear liquid oil.
 12. The solid lubricant composition of claim 1, consisting of from 0% to about 1% by weight of said optical brightener.
 13. The solid lubricant composition of claim 1, wherein said polylactic acid-based polymer is polyactide.
 14. A solid lubricant composition comprising: (a) from about 20% to about 70% by volume of polyactide; (b) from about 5% to about 75% by volume of at least one lubricant powder; (c) from 0% to about 20% by volume of at least one synthetic extreme pressure anti-wear liquid oil; and (d) from 0% to about 1% by volume of at least one optical brightener.
 15. The solid lubricant composition of claim 14, wherein said lubricant powder is selected from one or more of the group consisting of graphite and molybdenum disulfide.
 16. The solid lubricant composition of claim 15, wherein said lubricant powder consists of a mixture of 5 parts of molybdenum disulfide powder and 1 part graphite powder, by volume.
 17. The solid lubricant composition of claim 14, wherein said lubricant powder is selected from one or more of the group consisting of graphite, molybdenum disulfide, talc, mica and calcium carbonate.
 18. The solid lubricant composition of claim 14, consisting of about 1% to about 5% by volume of said synthetic extreme pressure anti-wear liquid oil.
 19. The solid lubricant composition of claim 14, consisting of from 0% to about 1% by weight of said optical brightener.
 20. A solid lubricant composition comprising: (a) from about 25% to about 70% by volume of at least one polymeric carrier, wherein at least a portion of said at least one polymeric carrier is selected from the group consisting of polylactic acid-based polymers and/or complex carbohydrates; (b) from about 5% to about 75% by volume of at least one lubricant powder; (c) from 0% to about 20% by volume of at least one synthetic extreme pressure anti-wear liquid oil; and (d) from 0% to about 1% by volume of an optical brightener. 